Electroacoustic transducers



Jan. 30, 1962 E. WEISS 3,019,304

ELECTROACOUSTIC TRANSDUCERS Filed Feb. 20, 1961 IN VEN TOR;

ATTORNEYS.

nite States This invention relates generally to electroacoustictransducers, and more particularly to a new and improved bone conductiontype of electroacoustic transducer having advantageous use in hearingaids or the like.

While electroacoustic bone conduction receivers are known and used inpresent day hearing aids, such prior art receivers have not provedentirely satisfactory for a number of reasons. In the past, where boneconduction receivers have been utilized in hearing aid eyeglasses forexample, it has been necessary to make certain adjustments duringfitting of the eyeglasses to provide sufficient static bias pressure tomaintain the receiver against the skin during dynamic excursions of thereceiver. This static bias pressure-typically about tenounces-heretofore has been provided by the compliance of the eyeglassesframe and/or the use of stiffening springs with the frame. Such bendingof the temples is a difiicult adjustment achieved by much trial anderror during the fitting of the hearing aid eyeglasses. In addition,there is the possibility that the static pressure will change with timeto alter the intelligibility of the hearing aid output.

A further disadvantage in the use of prior art bone conduction receiversarises from the use of a flat, rigid button member which makes contactwith the mastoid area. Because the rigid button member cannot conform tothe mastoid contour, a limited area of high contact pressure anddiscomfort is created. Also, since bone conduction response is afunction of the area of contact between the button member and themastoid, there is a possibility of variability in response with time asthe skin and bone tissue gradually yield under pressur to conform to theflat surface of the rigid button member.

In addition, the present day mounting of bone conduction receivers, asby means of rubber rings for example, may result in a high degree ofmechanical feedback transmission at those frequencies where peak forcesare developed, such as at 500 cycles and 1500 cycles. In the operationof the hearing aid rubber ring mount, the latter is severely compressedand may become quite stiff. This loss in resiliency causes vibration tobe transmitted to the temple case and in accordance with certain priorart practices, such vibratory feedback is reduced by the addition ofcertain masses to the temple case. Thus, it is known to utilize aberyllium copper casting and a lead weight at the bone conductionreceiver as well as an additional weight at the microphone to reduce thevibratory feedback in these instruments. Manifestly, this has resultedin heavy frame weights which, in turn, is a source of discomfort to thewearer of the hearing aid eyeglasses.

Accordingly, it is a general object of this invention to provide a newand improved bone conduction receiver adapted to eliminate thabove-described prior art difficulties.

In particular, it is an object of this invention to provide an improvedbone conduction receiver construction in which the desired staticpressure is developed automatically by pre-loaded torsion suspension ofthe receiver to thereby eliminate any need for frame adjustment.

It is another object of this invention to provide a new and improvedcontact button construction for a bone conduction receiver having theability to conform to the contour of the mastoid area upon contact toprovide uniformity of response at different shaped mastoids. Inaddition, it is an object of this invention to provide such tet ice

an improved contact button construction having a contact area muchlarger than that utilized in present day constructions to providegreater wearer comfort.

It is a further object of this invention to provide a new and improvedconduction receiver which utilizes torsion suspension plus highly dampedvibration absorbers tuned to particular frequencies to greatly reducethe over-all weight of the receiver and the support housing within whichit is mounted.

It is still another object of this invention to provide a new andimproved bone conduction receiver, as above, which is adapted to bemounted in a case so as to reduce mechanical vibratory feedback coupledto the case without the use of heavy physical reaction masses andwithout adversely affecting the low frequency response of the receiver.

It is a still further object of this invention to provide a novel boneconduction receiver having readily adjustable means for high and lowfrequency response and for providing the same low frequency response asprior bone conduction receivers with the use of less physical reactionmass.

It is still another object of this invention to provide a new andimproved bone conduction receiver which permits the use of smalleramplifiers, as by the elimination of the interstage transformersutilized in certain present-day hearing aid amplifier constructions.

The above and other objects are realized in accordance with the featuresof a specific illustrative embodiment of the invention which comprises apair of members hinged together at one end by a resilient hinge forrelative movement with respect to each other and pivotally mounted bypre-loaded torsion suspension means for movement with respect to thehearing aid case. One member is combined with a slidable mass surfacefor enabling ready adjustment of the low frequency response of thereceiver. The other member is combined with a slidable driving rodsurface for adjustment of the high frequency response of the receiver.Advantageously, a permanent magnet assembly is provided between the twomembers for establishing a proper DC. bias flux. A coil is wound in theform of an annulus surrounding the magnet and the bone receiver isadapted to be energized by the application of an alternating potentialacross the coil.

Further, in accordance with a feature of this invention, a compliantcontact button is mounted on the driving rod capable, when contactingthe mastoid, of conforming to the shape of the mastoid area without lossof response. As explained in greater detail hereinbelow, the compliantcontact button may take the form of a. flexible pouch or pillow filledwith a plurality of small particles to conform to the contour of themastoid area upon contact. Advantageously, the pouch is adapted to beformed with a relatively large contact area to nhance wearer comfort andvibration transmissibility.

The above and further novel features which are characteristic of theinvention are set forth with particularity in the appended claims. Theinvention itself, however, both as to its organization and operation,together with further objects and advantages thereof, will best beunderstood by reference to the following description taken inconjunction with the accompanying drawing in which:

FIGURE 1 is a perspective view of a hearing aid eyeglasses temple memberembodying the bone conduction receiver of the present invention;

FIGURE 2 is a cross-sectional view of the bone conduction receiver takensubstantially as shown along line 2-2 of FIGURE 1;

FIGURE 3 is a cross-sectional View of the bone conduction receiver takensubstantially as shown along line 3-3 of FIGURE 1;

FIGURE 4 is an exploded view of one illustrative embodiment of the boneconduction receiver in accordance with the invention; and

FIGURE 5 illustrates the bone conduction receiver of the invention inuse against the mastoid area of a hard of-hearing person.

Referring now to the drawing, and more particularly to FIGURE 1 thereof,there is shown a hearing aid eyeglasses temple member embodying thepresent invention. Those skilled in the art will appreciate that whilethe invention is not limited for use with a hearing aid eyeglassestemple member and finds many other equally advantageous uses, such ahearing aid eyeglasses temple member has been shown in this applicationfor purposes of illustration and explanation.

Thus, as shown in FIGURE 1, the hearing aid eyeglasses temple membercomprises an elongated casing, of a suitable light-weight material suchas plastic or aluminum, having a hinge member 12. at one end thereofsuitable for hinged connection to a hinge member in the front lens frameof the eyeglasses. The central portion of the temple member 14 may housea suitable sound pick-up microphone, an amplifier and a power sourcesuch as a battery. The rear portion of the temple member 10advantageously houses a bone conduction receiver 14 which is formed inaccordance with the principles of the present invention as explained ingreater detail hereinbelow. As illustrated in FIGURE 1, the portions ofthe bone conduction receiver 14 which protrude from the inner surface ofthe temple member casing comprise a large area contact button 16 adaptedto be positioned against the mastoid area of the wearer and an annularacoustic seal 18, surrounding but spaced from the contact button 16.

Reference is now made to FIGURES 2, 3, 4 and 5 for a more detaileddiscussion of the construction of the bone conduction receiver embodyingthe present invention. As there shown, the contact button 16advantageously takes the form of a resilient pouch or pillow 20 filledwith a plurality of small particles 21 to enable the contact button 16to conform to the contour of the mastoid area upon contact.

Those skilled in the hearing aid art are familiar with the deficienciesof the small, rigid contact buttons heretofore used in bone conductionhearing aids. The present invention, through the use of a large,resilient pouch filled with a plurality of small particles provides manyadvantages. Since the pouch 20 conforms to the mastoid contour, itprovides uniform contact pressure throughout the area of contact, hencegiving a greater uniformity of bone conduction receiver response. Itfurther serves to increase wearer comfort by the elimination of highcontact pressure areas. Further, the contact button 16 can be made withcontact areas of much greater size than that present in present-daydevices to further facilitate wearer comfort and receiver etficiency.

In practice, it has been found advantageous to construct such a contactbutton 16 with a resilient pouch 20 formed of a suitable plasticmaterial such as vinyl and to utilize spherical glass beads within thepouch 29, as illustrated by the small spherical particles 21. Thecontact button 16 advantageously is mounted on a pedestal platform 22.In one preferable embodiment of the invention, it has been founddesirable to form the pedestal platform 22 of a suitable light-weightmaterial, such as aluminum, having a surface area approximately the sameas the lower surface of the contact button 16.

The pedestal platform 22 is mounted on a pedestal 24, also of a suitablelight-weight material such as aluminum, which in turn is supported bythe upper magnetic pole piece 26. In accordance with a salient featureof this invention, the receiver comprises a pair of magnetic pole pieceshaving resilient hinge means connected to one end of each of the polepieces to position the latter in spaced, vibratable relation relative toeach other.

This unique construction is embodied in the illustrated device by meansof the upper magnetic pole piece 26, the lower magnetic pole piece 28,and the resilient hinge member 3% connected to one end of each of saidpole pieces. As more clearly illustrated in FIGURE 4 of the drawing, theupper magnetic pole piece 26 comprises a generally rectangular arm 32having an off-set shoulder 34 at one end thereof. Similarly, the lowermagnetic pole piece 28 comprises a generally rectangular arm 36 havingan offset shoulder 38 at one end thereof. The resilient hinge member 30advantageously is comprised of a U-shaped spring member, preferably ofmagnetic steel, which is adapted to fit over off-set shoulder portions34 and 38 of the magnetic pole pieces so as to provide a compact,magnetic assembly structure.

Each magnetic pole piece may be secured to the resilient hinge 30 by asuitable fastening means, as for example, by means of the threadedapertures and screws shown in FIGURES 2, 3, and 4 of the drawing. Thus,the upper magnetic pole piece 26 may be securely fastened to the upperarm of resilient hinge 30 by means of the threaded fasteners 40, and ina similar manner, the lower magnetic pole piece 36 may be securelyfastened to the lower arm of resilient hinge 30 by means of the threadedfasteners 42. When the magnetic structure is assembled, as illustratedin FIGURE 3 of the drawing, the upper and lower magnetic pole pieces arein spaced relation relative to each other to define an air gaptherebetween, and are adapted for vibration relative to each other inresponse to exciting current from the hearing aid amplifier.

A magnet 44 is mounted on the lower pole piece 28 so as to be positionedin the air gap between the spaced pole pieces. Advantageously, themagnet 44 may be a cylinder of a suitable magnetic material such asAlnico 5 or the like. An electrically energizable exciting coil 46 woundon a suitable bobbin 48 is positioned around the magnet 44 such thatenergization of coil 46 by the application of exciting current at thecoil terminals 50 and 52 causes the upper magnet pole piece 26 to bevibrated relative to the remainder of the magnetic assembly at afrequency and with amplitude determined by the characteristics of theexciting current.

Thus, those skilled in the art will appreciate that if the output of ahearing aid amplifier is connected to the coil terminals 50 and 52, thecontact button 16 will be vibrated against the mastoid area of thewearer in a manner corresponding to the sound waves detected andamplified by the hearing aid.

In the construction and assemby of the present invention, it has beenfound advantageous to magnetize the magnet 44 after the magneticstructure has been assembled in the manner described hereinabove. Thisresults in the use of less magnetic material which is of great advantagein reducing the cost of construction and in reducing the over-all weightof the hearing aid.

In accordance with a further feature of this invention, a highlydesirable degree of low frequency response can be obtained with asmaller physical reaction mass than that required in the prior art boneconduction hearing aids. Towards this end, the lower magnetic pole piece28 forms a part of the reaction mass of the receiver and an additionalreaction mass 54 is adjustably positioned at one end of the lowermagnetic pole piece 28 to permit selective adustment of the lowerfrequency response. The additional reaction mass 54, which may be formedof lead for example, advantageously is provided with one or more pins 56extending therefrom and the lower magnetic pole piece 28 is formed witha suitable elongated aperture 58 for slidably receiving each pin 56 ofthe reaction mass 54. As a result of this construction, the additionalreaction mass 54 may selectively be moved toward or away from the lowermagnetic pole piece 28 to enable adjustment of the receiver lowfrequency response.

netic pole piece 26. The upper magnetic pole piece 26 may be providedwith a plurality of spaced, threaded openings 60 adapted to receive asuitable threaded fastener 62 which is positioned through the pedestalplatform 22 and the pedestal 24 to fasten the platform, pedestal andupper magnetic pole piece together. Thus, as particularly illustrated inFIGURE 3, for example, the threaded fastener 62 may selectively bepositioned in any of the internally threaded openings 60 upon assemblyof the receiver to adjust the high frequency response to a desiredcharacteristic.

While the particular embodiment of the invention i1- lustra-ted in thedrawings has been shown with a slidable adjustment for low frequencyresponse and a discrete adjustment for high frequency response, it willbe obvious to those skilled in the art that these adjustments may bemade either continuously or discretely variable as desired, fully withinthe spirit and scope of the present invention.

In accordance with a highly important feature of this invention, themagnetic structure and contact button assembly of the receiver ismounted in a hearing aid case by unique pre-loaded torsion suspensionmeans to provide a desired amount of static bias pressure of thereceiver against the mastoid area of the wearer. This novel preloadedmounting of the receiver provides the desired bias pressure independentof frame stiffness adjustment in an eyeglasses hearing aid to therebyeliminate any stressing or bending of the plastic parts of theeyeglasses temple members as now required in contemporary boneconduction hearing aid eyeglasses,

This highly important characteristic of the present invention isachieved in the illustrated embodiment by means of the annular rubbertorsion mounts 64 and 66 which are sandwiched between the hearing aidreceiver and the hearing aid case.

As particularly illustrated in FIGURES 2 and 4 of the drawing, suitablefender members 68 and 70 may be secured as by soldering, to oppositesides of the upper magnetic pole piece 26, but free of the lowermagnetic pole piece 28, for receiving the annular torsion mounts 64 and66. The internal side walls of the hearing aid case 10 may be suitablyrecessed, as at 72 and 74, to receive the annular torsion mounts 66 and64, respectively. In the assembly of the receiver into the case, theannular torsion mounts 64 and 66 are positioned within the wall recesses72 and 74 and are adhesively fastened thereto in a manner so as toautomatically provide a pro-selected loading pressure of the contactbutton 16 against the mastoid area when the hearing aid is in wearingposition.

Those skilled in the art will readily appreciate that other types oftorsion mounts, such as a suitable torsion spring, could be used in lieuof the annular rubber torsion mounts 64 and 66. In practice, it has beenfound that the receiver should be mounted in the case with about 10ounces of static bias pressure to insure that the receiver does notleave the head or the skin during dynamic excursions of the receiver.Heretofore, this static bias pressure has been provided by thecompliance of the eyeglasses frame and/or stiffening springs, but thepresent invention eliminates these unsatisfactory prior art means forproviding the desired static bias pressure.

It is a still further feature of this invention to provide the receiverwith a suitable acoustic sealing means around the contact button 16 sothat when the contact button is depressed against the mastoid areaasillustrated in FIG- URE 5an eificient acoustic seal is provided againstthe head of the wearer. In accordance with this embodiment of theinvention, a fluid filled annular member 18 is positioned on the hearingaid case so as to completely surround the contact button 16. As shown inFIGURE 3, the contact button 16 normally extends above the acoustic seal18 when the hearing aid is not in wearing position due to the pro-loadedstatic bias pressure afforded by the torsion mount describedhereinabove. However, when the hearing aid is positioned against themastoid area, as illustrated in FIGURE 5, the contact button 16 isdepressed against its torsion mount to provide the desired static biaspressure against the mastoid area and the annular acoustic seal 18provides high acoustic attenuation to acoustic radiation emanating fromthe vibrating element.

While there has been shown and described a specific embodiment of thepresent invention, it will, of course, be understood that variousmodifications and alternative constructions may be made withoutdeparting from the true spirit and scope of the invention. Therefore, itis intended by the appended claims to cover all such modifications andalternative constructions as fall within their true spirit and scope.

What is claimed as the invention is:

l. The improvement of an electroacoustic bone conduction receivercomprising first and second magnetic pole members, resilient hinge meansconnected to one end of each of said pole members to position said polemembers in spaced, vibratable relation relative to each other,electrically energizable electromagnetic means positioned on said firstpole member and in operative association with said second pole membersuch that energization of said electromagnet means provides vibration ofsaid sec ond pole member relative to said first pole member at afrequency determined by the energizing current, a reaction masssupported by said first pole member and relatively movable thereon forenabling adjustment of the low frequency response of said boneconduction receiver, a contact button mounted on said second pole memberfor vibration therewith against the skin of the wearer, said contactbutton comprising a resilient pouch filled with a plurality of smallparticles to enable said contact button to conform to the surfacecontour of the skin, selectively movable support means for supportingsaid contact button on said second pole member and for enablingadjustment of the high frequency response of said bone conductionreceiver, and torsion mounting means attached to said receiver formounting the latter within a case with a desired biasing force againstthe skin of the wearer.

2. The improvement of an electroacoustic bone conduction receivercomprising first and second magnetic pole members, resilient hinge meansconnected to one end of each of said pole members to position said polemembers in spaced, vibratable relation relative to each other,electrically energizable electromagnetic means positioned on said firstpole member and in operative association with said second pole membersuch that energization of said electromagnet means provides vibration ofsaid second pole member relative to said first pole member at afrequency determined by the energizing current, a contact button mountedon said second pole member for vibration therewith against the skin ofthe wearer, said contact button comprising a resilient pouch filled witha plurality of small particles to enable said contact button to conformto the surface contour of the skin, and torsion mounting means attachedto said receiver for mounting the latter within a case with a desiredbiasing force against the skin of the wearer.

3. The improvement of an electroacoustic bone conduction receivercomprising first and second magnetic pole members, resilient hinge meansconnected to one end of each of said pole members to position said polemembers in spaced, vibratable relation relative to each other,electrically energizable electromagnetic means positioned on said firstpole member and in operative association with said second pole membersuch that energization of said electromagnet means provides vibration ofsaid second pole member relative to said first pole member at afrequency determined by the energizing current, and a contact buttonmounted on said second pole member for vibration therewith against theskin of the wearer, said contact button comprising a resilient pouchfilled with a plurality of small particles to enable said contact buttonto conform to the surface contour of the skin.

4. The improvement of an electroacoustic bone conduction receivercomprising first and second magnetic pole members, resilient hinge meansconnected to one end of each of said pole members to position said polemembers in spaced, vibratable relation relative to each other, electrically energizable electromagnetic means positioned on said first polemember and in operative association with said second pole member suchthat energization of said electromagnet means provides vibration of saidsecond pole member relative to said first pole member at a fre quencydetermined by the energizing current, and a contact button mounted onsaid second pole member for vibration therewith against the skin of thewearer.

5. The improvement of an electroacoustic bone conduction receivercomprising first and second magnetic pole members, resilient hinge meansconnected to one end of each of said pole members to position said polemembers in spaced, vibratable relation relative to each other,electrically energizable electromagnetic means positioned on said firstpole member and in operative association with said second pole membersuch that energization of said electromagnet means provides vibration ofsaid second pole member relative to said first pole member at afrequency determined by the energizing current, a contact button mountedon said second pole member for vibration therewith against the skin ofthe wearer, and torsion mounting means attached to said receiver formounting the latter within a case with a desired biasing force againstthe skin of the wearer.

6. The improvement of an electroacoustic bone conduction receivercomprising first and second magnetic pole members, resilient hinge meansconnected to one end of each of said pole members to position said polemembers in spaced vibratable relation relative to each other,electrically energizable electromagnetic means positioned on said firstpole member and in operative association with said second pole membersuch that energization of said electromagnet means provides vibration ofsaid second pole member relative to said first pole member at afrequency determined by the energizing current, a reaction masssupported by said first pole member and rela tively movable thereon forenabling adjustment of the low frequency response of said boneconduction receiver, a contact button mounted on said second pole memberfor vibration therewith against the skin of the wearer, and selectivelymovable support means for supporting said contact button on said secondpole member and for enabling adjustment of the high frequency responseof said bone conduction receiver.

7. The improvement of an electroacoustic bone conduction receivercomprising first and second magnetic pole members, resilient hinge meansconnected to one end of each of said pole members to position said polemembers in spaced, vibratable relation relative to each other,electrically energizable electromagnetic means positioned on said firstpole member and in operative association with said second pole membersuch that energization of said electromagnet means provides vibration ofsaid second pole member relative to said first pole member at afrequency determined by the energizing current, a resilient contactbutton mounted on said second pole member for vibration therewithagainst the skin of the wearer, said contact button having a relativelylarge surface area adapted to conform to the surface contour of theskin, and torsion mounting means attached to said receiver for mountingthe latter within a case with a desired biasing force against the skinof the wearer.

8. The improvement of an electroacoustic bone conduction receivercomprising first and second magnetic pole members, resilient hinge meansconnected to one end of each of said pole members to position said polemembers in spaced, vibratable relation relative to each other,electrically energizable electromagnetic means positioned on said firstpole member and in operative association with said second pole membersuch that energization of said electromagnet means provides vibration ofsaid second pole member relative to said first pole member at afrequency determined by the energizing current, a resilient buttonadapted to conform to the contour of the skin mounted on said secondpole member for vibration therewith against the skin of the wearer,acoustic sealing means positioned around said resilient contact buttonfor attenuating acoustic radiation from said receiver when the contactbutton is positioned against the skin of the wearer, and torsionmounting means attached to said receiver for mounting the latter withina case with a desired biasing force against the skin of the wearer.

9. The improvement of an electroacoustic bone conduction receivercomprising first and second magnetic pole members, resilient hinge meansconnected to one end of each of said pole members to position said polemembers in spaced, vibratable relation relative to each other,electrically energizable electromagnetic means positioned on said firstpole member and in operative association with said second pole membersuch that energization of said electromagnet means provides vibration ofsaid second pole member relative to said'first pole member at afrequency determined by the energizing current, a reaction masssupported by said first pole member and relatively movable thereon forenabling adjustment of the low frequency response of said boneconduction receiver, a contact button mounted on said second pole memberfor vibration therewith against the skin of the wearer, selectivelymovable support means for supporting said contact button on said secondpole member and for enabling adjustment of the high frequency responseof said bone conduction receiver, acoustic sealing means positionedaround said contact button and effective when the contact button ispositioned against the skin of the wearer to attenuate undesirableacoustic radiation from said receiver, and torsion mounting meansattached to said receiver for mounting the latter within a case with adesired biasing force against the skin of the wearer.

10. The improvement of an electroacoustic bone conduction receivercomprising first and second magnetic pulse members, resilient hingemeans connected to one end of each of said pole members to position saidpole members in spaced, vibratable relation relative to each other,electrically energizable electromagnetic means positioned on said firstpole member and in operative association with said second pole membersuch that energization of said electromagnet means provides vibration ofsaid second pole member relative to said first pole member at afrequency determined by the energizing current, a resilient, skinconforming, contact button mounted on said second pole member forvibration therewith against the skin of the wearer, a fender securelyattached to each side of said second pole member, and annular rubbertorsion members attached to said fenders for mounting the receiverwithin a case with a desired biasing force against the skin of thewearer.

No references cited.

